Split a file into numbered parts
Pick any file and break it into smaller chunks by size or by count. Each part is downloaded with the original extension preserved. Runs entirely in your browser.
Pick a file to split
How to split a file
Break a single file into numbered byte-aligned parts that can be re-stitched with File Joiner — preserves extension for round-trip work.
- 01
Pick a file
Anything that fits in browser memory.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
inpututf-8client-sidevalidatedfile · textany · setarchive.zip
loaded · parsedclient-side - 02
Choose mode
By size (KB/MB) or by total part count.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
modeoptionslivememoisedtogglesmode · memoisedsize · live1 MB chunks
options set · memoisedlive - 03
Preview parts
See each numbered part with its byte length.
Randomness — where used — comes from
crypto.getRandomValues, neverMath.random. Heavy work sits inuseMemo.previewcomputeinstantlocaldeterministicparts · instantn · computedfile.part-01.bin
computed · instantinstant - 04
Download all
Staggered downloads at 250ms intervals to avoid pop-up blocking.
Copy writes through
navigator.clipboardand downloads use aBlob— zero network traffic. Same input plus same options always yield the same bytes.exportcopydownloadzero-networkreproducibleok · copiedready · copiedqueued
shipped · ready to shipsuccess
Pro tips for everyday utilities
Reach for crypto.getRandomValues
Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.
Mock data with seeds
Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.
Reference cards beat memory
Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.
Browser APIs vary
Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.
Persist in the right place
localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.
When to split a file
Email caps, upload limits, chunked transfers.
Email size limits
Slice an attachment under a 25 MB cap. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.
CSPRNG-backedUpload caps
Break a file into form-sized chunks. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.
reproducibleResumable downloads
Produce parts a client can fetch and stitch. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.
snappyTesting chunkers
Create known-shape inputs for chunk-processing code. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.
feature-detectedSide-channel transfer
Move data across constrained pipes piece by piece. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.
deterministicArchive sharding
Split large archives across multiple disks. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.
production-readyFrequently asked questions
Something missing?
Tell us what you need. We ship the top requests every two weeks.